Within recent years a relatively simple method has been developed for welding together non-ferrous materials, particularly aluminum and copper. According to this method, two sections or bars of metal are made to flow together at room temperature by merely applying sufficient pressure at the juncture thereof, with no heat applied to bring about a weld. Although this method has been known and practiced for some time, it has been limited to the softer aluminum alloys and to parts having small cross-sectional areas (usually less than 0.5 square inches of cross-sectional area).
The aforementioned rather simple cold welding process, while suitable for the softer aluminum alloys and members of small cross-sectional areas, is not suitable for higher strength aluminum and magnesium alloys or for aluminum and magnesium members having a large cross-sectional area.
Many of these high strength alloys are far too brittle, particularly those of large cross-sectional area, to permit the extreme distortion and deformation necessary for cold pressure welding. This has presented a particularly troublesome problem, not only in non-heat treatable high strength alloys, such as aluminum alloys (for example those containing 0.3% silicon, 0.4% iron, 0.1% copper, 0.05% to 0.2% manganese, 4.5% to 5.6% magnesium, 0.05% to 0.2% chromium, 0.1% zinc, remainder aluminum and especially the high strength heat treatable aluminum alloys such as those which have the standard designations 2014, 2017, 6061, 7075, 2024, 5056) and magnesium alloys (such as those containing:
1. 3.0% ALUMINUM, 0.45% MANGANESE, 1% ZINC, REMAINDER MAGNESIUM;
2. 5.7% ZINC, 0.55% ZIRCONIUM, REMAINDER MAGNESIUM); AND IN ALLOYS OF SIMILAR METALLURGICAL CHARACTERISTICS.
Moreover, it has been practically impossible to obtain strong ductile welds in these alloys without post weld heat treatment. Such post weld heat treatment is cumbersome and impractical, and gives rise to undue distortion of the components. Even where post weld heat treatment has been possible, difficulties have been encountered in the form of weld cracking and low ductility. This problem is particularly acute in the aircraft and allied industries where large quantities of both high strength aluminum and magnesium alloys, and also, aluminum and magnesium alloys having large cross-sectional areas are utilized.
It is therefore an object of this invention to present a simple and effective process for the butt welding of high strength aluminum and magnesium alloys. A further object of this invention is to present a simple and effective process for the butt welding of high strength aluminum alloys to high strength magnesium alloys. Another object of this invention is to present a process for butt welding aluminum and magnesium alloys of large cross-sectional areas. A further object of this invention is to present a process for welding high strength aluminum and magnesium alloys wherein joint efficiencies of 85% to 100% are obtained. An additional object of this invention is to present a process for welding high strength aluminum alloys to high strength magnesium alloys wherein a ductile weld is produced which is not brittle and which presents no metallurgical notch effect. Another object of this invention is to present a process of welding aluminum and magnesium alloys which will permit the design of higher strength structures utilizing the higher strength alloys and/or a wide range of cross-sectional areas.
Various other features, objects and advantages of the invention will appear from the drawings taken in conjunction with the description, although it should be clearly understood that the invention is not limited to the specific details set forth.